1. Field of the Invention
This invention relates generally to automatic test equipment used in the manufacture of semiconductors and more specifically to the production interface and handler drivers of the test system
2. Description of the Related Art
Automatic test equipment is widely used in the manufacture of semiconductors. Semiconductors are generally tested at least once during their manufacture and are sometimes tested at more than one step in the manufacturing process. Because every component is tested, speed of testing is critical to the economic manufacture of semiconductors. Slow testing prevents full utilization of the expensive capital equipment needed to produce semiconductor components. Modern semiconductor components are very complicated and have many operating states. Each of these operating states must be exercised to perform a complete test. Automatic test equipment is therefore designed to apply test data to a semiconductor device and make numerous measurements very quickly in a production setting.
FIG. 1 shows a generalized automatic test system of the prior art. To provide thorough and fast testing, the automatic test system generally includes a tester body 112, a computerized work station 110 and a handling device 114. The computer work station 110 controls both the handling device 114 and the tester body 112. It controls the handling device 114 to position the semiconductor device (not shown) where it makes contacts with numerous test probes 118 on the tester body 112. Often, a tester will include a separate test head containing test probes 118. However, such a distinction is not important for the invention.
Workstation 110 then controls tester body 112 to run a series of tests on the device under test. Each test generally includes a setup portion in which control signals are sent from the work station 110 to the tester body 112. The control signals are usually digital values sent over bus 116. These control signals configure the hardware within tester body 112 to make the measurements required for the test The hardware within the tester body provides stimulus and measures responses from the device under test in accordance with the control signals.
FIG. 1 shows that the hardware within tester body 112 includes numerous circuits identified as pins 124. Each pin 124 generates signals or makes measurements for one of the test probes 118. Each pin might provide or measure a static, or DC, signal. Alternatively, each pin 124 might provide or measure changing data in what is sometimes called a "burst".
During a burst, tester body 120 is controlled by timing and sequencing circuit 120. Timing and sequencing circuit 120 causes each of the pins 124 to read a sequence of data values from an associated memory 128. Each data value indicates the type of signal the pin should apply or expect to measure at its associated test probe 118 at a specific point in time. If the pin compares a measurement to an expected value, the results might also be stored in memory 128.
The set of data values that define the values all the pins 124 should provide or expect to measure at one time is called a "vector." During a burst, many vectors are executed. The vectors must be executed at a very high rate to simulate actual operating conditions of the device under test. There are usually millions of vectors to define the bursts needed to test a semiconductor device. The vectors are typically loaded into memories 128 at the time test system is programmed to test a particular type of part. This loading process might take several minutes and is not repeated for each burst. Rather, for each burst, work station 110 sends commands indicating which vectors are to be executed as part of the burst. Once the burst is completed, work station 110 reads the results of the burst from memory 128 or timing and sequencing circuit 120.
In addition, tester body 112 includes one or more instruments 126. An instrument performs a specific test function. It might for example generate a specific test signal such as a sine wave. Alternatively, an instrument might sample a signal at a high rate so that it can later be analyzed by a digital signal processor. These functions might be performed as part of a burst or might be performed separate from a burst.
A full test of a part, sometimes called a "job", will consist of a series of bursts interspersed with DC measurements or measurements by instruments 126. The bursts might be used to measure specific functional attributes of the device under test. Alternatively, each burst might be used only to place the device under test into a state in which a DC measurement can be taken. The order in which these elements of a test are performed, sometimes called the "flow," is dictated by software in workstation 110.
Once a device has been fully tested, or tested to the point where it is determined to be defective, work station 110 generates control signals to the handling device 114. Handling device 114 then presents the next device to be tested to tester body 112 and the process is repeated. Work-station 110 also gathers data about whether particular devices passed or failed. It can process this data so that defective devices are discarded or it can perform other functions, such as analyzing the data for failure trends.
For production it is highly desirable that the software that allows an operator to control the tester be very easy to learn and use. What is needed in a production test environment, is a very simple operator interface interface to the rest of the test system. In addition the interface must be flexible and easy to change because of the many varied requirements of this interface from customer to customer.